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Related to Donnan equilibrium: Nernst equation
Donnan equilibrium[′dō·nən ē·kwə′lib·rē·əm]
The particular equilibrium set up when two coexisting phases are subject to the restriction that one or more of the ionic components cannot pass from one phase into the other; commonly, this restriction is caused by a membrane which is permeable to the solvent and small ions but impermeable to colloidal ions or charged particles of colloidal size. Also known as Gibbs-Donnan equilibrium.